Consolidation of calcium phosphate powder through microwave sintering / Natasha Ahmad Nawawi, Ramesh Singh and Tan Chou Yong

In the last 50 years, the major drawback of HA ceramic usage in clinical applications is its inherent brittleness and lower mechanical strength than those of cortical bone. This is turn calls for the development of dense nanostructured HA with the major concern is to enhance densification while limiting its grain growth. Hence, a promising way to obtain this could be a fabrication of fully dense nanostructured materials through sintering process. In this work, eggshell derived hydroxyapatite (HA-Es) powder has been prepared via solid state sintering and its sinterability was investigated through microwave sintering at various sintering temperatures (950-1250 °C). The phase stability, microstructural evolution and relative density of HA-Es were deliberated. The results indicate that microwave sintering regime has been successfully employed and this short sintering regime did not promote extensive grain growth even when sintered at high temperature

Electroplating Jig Design for Mild Steel Nut for Cobalt Alloy Plating

This partly ongoing research focuses on designing a stainless-steel jig holder for varied sizes of mild steel nuts for cobalt alloy plating, scaled to industry-level requirements for field testing. The chosen type of electroplating jig is rack plating. The modelling and analysis of the design were done using SolidWorks software, which included 3D design and finite element analysis. The result shows the strength of the jig holder is reliable for nut sizes ranging from M8 to M16. In conclusion, the jig holder performance has been successfully optimized based on the material and design chosen for its simulation. Keywords: Cobalt-Alloy Plating; Electroplating; Modelling; Finite Element Analysis eISSN: 2398-4287© 2022. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians/Africans/Arabians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. DO

Effects of Solvents on ZnO Nanoparticles Synthesis via Sol–gel Method

Zinc oxide nanoparticles have been prepared by the sol-gel method at different solvent (methanol (MeOH), ethanol (EtOh) and distilled water) and at different calcination temperatures (700 °C, 800 °C and 900 °C). The phase and microstructure of the prepared ZnO powder were investigated. ZnO powder were characterized by using XRD, EDX and FESEM. XRD analysis shows ZnO exhibited a hexagonal (wurtzite) structure with crystallite sizes 34.146 nm, 34.283 nm, and 34.523 nm and FESEM micrographs show that synthesized ZnO has a nanorod-like structure with an average particle size, 113.716 nm, 125.825 nm, and 141.725 nm for solvent methanol, ethanol and distilled water and calcination temperature of 700 °C, 800 °C and 700 °C respectively. The obtained ZnO nanoparticles are homogenous and consistent in size, corresponding to the XRD results that exhibit good crystallinity. EDX analysis shows pure ZnO with different solvents at 700 °C calcination temperatures. The surface of the ZnO also exhibits elements of O and Zn. This result has confirmed that the ZnO nanoparticles has high purity. Based on the analysis from the XRD and FESEM test, the best solvent with the best calcination temperature has been chosen, which is Methanol at 700 °C

Properties of calcium phosphate bioceramic prepared by solid state and chemical route / Natasha Ahmad Nawawi

In this research, a simple solid state sintering was successfully employed to synthesize highly crystalline, high purity and single phase nanostructured hydroxyapatite powder using waste eggshells (HA-Es). The process involved mixing calcined eggshell powder and dicalcium hydrogen phosphate di-hydrate followed by a heat treatment at 800 °C. The resultant flower-like morphology of HA-Es powder exhibited excellent sintering characteristics. Besides that, pure HA was also synthesized using commercial chemical as Ca precursors through two chemical methods that are wet chemical precipitation (HA-Wp) and sol-gel (HA-Sg) for comparison study. In conventional pressureless sintering, HA-Es was able to retain the single HA phase stability until 1250 °C. The optimum sintering temperature for HA-Es was 1250 °C with the overall best combination of properties being recorded: relative bulk density of 97.7 %, Vickers hardness of 5.62 GPa, excellent fracture toughness of 1.51 MPam1/2 and average grain size was below 1 μm (0.950 μm). In contrast, the optimum sintering temperature of HA-Wp was 1200 °C with a bulk density of 97.9 %, Vickers hardness of 4.8 GPa, fracture toughness of 1.29 MPam1/2 and average grain size of 1.62 μm. In addition, the overall structural characterization and relative density of HA-Wp were significantly better than that of the HA-Sg. In microwave sintering, HA-Es was able to retain the HA phase stability up to 1200 °C and this is regarded as the optimum sintering temperature with the following properties: relative bulk density of 96.0 %, Vickers hardness of 3.65 GPa, fracture toughness of 1.05 MPam1/2 and average grain size of 2.08 μm. Meanwhile for HA-Wp, the optimum sintering temperature was 1100 °C with a bulk density of 96.9 %, Vickers hardness of 3.82 GPa, fracture toughness of 0.86 MPam1/2 and average grain size of 0.85 μm. Overall, these result revealed that the sinterability and mechanical properties of the HA-Es produced by the conventional sintering method were significantly better than HA-Es produced by microwave sintering method. Basically, the hardness and fracture toughness of all HA samples were initially influenced by the increase in relative density with sintering temperature until they reached a maximum value at a critical grain size limit (dc). Above this critical limit, grain growth acts as the controlling parameter. Therefore, the properties then decreased with increasing grain size despite exhibiting high bulk density. Both in vitro dissolution study in PBS and cell culture investigations confirmed that conventionally sintered eggshell derived HA exhibited excellent biological performance. In this work, sintered HA-Es at 1250 °C was found to have the best cell response and also improved mechanical properties. It can be suggested that the mechanical properties and the efficiency of HA in cell response are grain size dependent activities. Smaller grain size will induce an increase in grain boundary at the surface and therefore facilitates the cells to proliferate. Thus, this research proved that HA synthesized from waste eggshell through solid state method could be a potential bioceramic for use in the clinical application

Calcium phosphate nanoparticles prepared via solid-state route

To date, the direction of bioceramic research is focused on the improvement of the mechanical performance and biological properties of existing bioactive ceramics particularly HA. Hence, the synthesis of crystalline HA nanoparticles with expected microstructure is of primary importance because the process directly relates to the phase purity, morphology, and particle size of the final HA particles. In this work, a simple and cost-effective technique, solid state reaction method was successfully employed to synthesize highly crystalline, high purity and single phase nanostructured hydroxyapatite powder using waste eggshells (HA-Es). The process involved mixing calcined eggshell powder and dicalcium hydrogen phosphate di-hydrate followed by a heat treatment at 800 °C for 5 hours. The resultant flower-like nanostructure HA powder is composed of leaf-like flakes having 100-200 nm width and crystallite size calculated using XRD data of ~56.21 nm

Dense manganese doped biphasic calcium phosphate for load bearing bone implants

Dense pure biphasic calcium phosphate (BCP) and Mn-doped BCP ceramics were fabricated via uniaxial pressing using the sol-gel derived powders. The compacted discs were sintered in air atmosphere with temperatures ranging from 1000 ºC to 1400 ºC. All powders have been proved to show HA and β-TCP phases only. Manganese doping improves the densification in the BCP structure as the relative density increased with Mn doping and also sintering temperature. Considerable grain growth has been observed at 1300 ºC for Mn-doped BCP samples compared to the pure BCP. 15 mol% Mn showed the maximum hardness value of 6.66 GPa at 1400 ºC compared to pure BCP of only 2.89 GPa. Similarly, the Mn-doped BCP has superior fracture toughness where it attained maximum values of 1.05 MPam1/2 at 1400 ºC compared to 0.72 MPam1/2 at 1300 ºC of pure BCP. In a nutshell, Mn doping has successfully brought improvement in the mechanical properties of the BCP

Effects of manganese doping on the dielectric properties of titanium dioxide ceramics

We have investigated the effect of manganese (Mn) doping on properties of nanosized biphasic calcium phosphate powders and their dense bodies. Manganese levels of 0.6, 1.3, 1.9, 4.3, 7.0 and 11.9 at.% were successfully incorporated into biphasic calcium phosphate via a sol–gel route. The prepared powders were calcined at temperatures of 500–1200 °C. The X-ray diffraction analysis revealed that a mix phase comprising of hydroxyapatite and β-tricalcium phosphate were present, however the content of each phases in the structure was affected by the Mn content. The studies found that the largest portion of β-tricalcium phosphate was detected at 4.3 at.% Mn doping. The incorporation of Mn has also greatly increased the crystallinity of the biphasic calcium phosphate powder due to progressive densification of particles. Characterization on their sintered dense bodies showed that manganese concentration affected the physical properties of the dense bodies. The highest density was found for 4.3 at.% Mn doped biphasic calcium phosphate sintered at 1300 °C

Synthesis and properties of biphasic calcium phosphate prepared by different methods

Hydroxapatite (HA) is a stable phase with low dissolution rate in body fluid. Meanwhile, β-tricalcium phosphate (β-TCP) is rather soluble but the dissolution rate is too fast for bone bonding. Therefore a mixture of both is desirable to control the bioresorbability. In this work, calcium phosphate powder has been synthesized via sol gel and wet precipitation method to compare phase behaviour of these powders upon calcination. XRD result clearly revealed that both as-synthesized powders were pure HA with good purity. The decomposition of HA to TCP took place in the range of 700-800 °C and 800-900 °C for sol gel and wet chemical precipitation powder, respectively. The weight loss detected at 700-850°C in TGA analysis confirmed the presence of this biphasic mixtures. From FTIR analysis, profound change in OH- band intensity was attributed to the increased in HA crystallinity with calcination temperature

Sintering and properties of dense manganese-doped calcium phosphate bioceramics prepared using sol-gel derived nanopowders

Dense manganese-doped biphasic calcium phosphate (Mn-BCP) ceramics were fabricated via uniaxial pressing using the sol-gel derived powders. The compacted discs were sintered in ambient atmosphere with temperatures ranging from 800�C to 1400�C. Manganese (Mn) level was varied in the range of 0.6, 1.9, 4.3, and 11.9mol%, and its effect on physical and mechanical properties of the dense samples were investigated. All dense samples have been proved to show HA and �-TCP phases only. Mn doping has shifted the onset of the sintering temperature of the BCP, leading to the improved densification of BCP ceramics. The relative density also increased with sintering temperature. Considerable grain growth has been observed for Mn-doped BCP samples when compared to the undoped BCP. Furthermore, 11.9mol% Mn-doped BCP dense samples showed the maximum hardness of 6.66GPa compared to 2.89 GPa for the undoped BCP. The incorporation of Mn was also found to be beneficial in enhancing the fracture toughness of BCP throughout the temperature range employed. This study has shown that Mn doping was effective in improving the sintering properties of BCP without affecting the phase stability

Sintering and properties of dense manganese-doped calcium phosphate bioceramics prepared using sol-gel derived nanopowders

Dense manganese-doped biphasic calcium phosphate (Mn-BCP) ceramics were fabricated via uniaxial pressing using the sol-gel derived powders. The compacted discs were sintered in ambient atmosphere with temperatures ranging from 800�C to 1400�C. Manganese (Mn) level was varied in the range of 0.6, 1.9, 4.3, and 11.9mol%, and its effect on physical and mechanical properties of the dense samples were investigated. All dense samples have been proved to show HA and �-TCP phases only. Mn doping has shifted the onset of the sintering temperature of the BCP, leading to the improved densification of BCP ceramics. The relative density also increased with sintering temperature. Considerable grain growth has been observed for Mn-doped BCP samples when compared to the undoped BCP. Furthermore, 11.9mol% Mn-doped BCP dense samples showed the maximum hardness of 6.66GPa compared to 2.89 GPa for the undoped BCP. The incorporation of Mn was also found to be beneficial in enhancing the fracture toughness of BCP throughout the temperature range employed. This study has shown that Mn doping was effective in improving the sintering properties of BCP without affecting the phase stability